The Independent Police Complaints Commission is to investigate the conduct of a chief of police and his deputy arrested over corruption claims.
Chief Constable of Cleveland Sean Price and his deputy Derek Bonnard were arrested earlier this month and held on suspicion of misconduct in a public office, fraud by abuse of position and corrupt practice.
Police watchdog the IPCC was brought in after being referred allegations by Warwickshire Police detectives leading the probe.
An IPCC senior investigator will now work alongside the Chief Constable of Warwickshire Police, Keith Bristow, to manage the element of the investigation into potential misconduct or gross misconduct by Mr Price, DCC Bonnard, and a third person arrested - the force's former head of legal services, Caroline Llewellyn.
Mr Bristow will remain in charge of the investigation into criminal matters.
The three were arrested in dawn raids at their homes on August 3 and suspended from their posts soon afterwards.
IPCC Commissioner Nicholas Long said: "Allegations of corruption within a police force have a significant impact on public confidence and must be investigated thoroughly.
"I am confident Mr Bristow and his team are being thorough in their approach.
"While I believe it important that the IPCC becomes involved to provide wholly independent oversight, I also believe it important that we do not do anything that might undermine the ongoing investigation.
"It is for this reason that I have decided it appropriate for one of our senior investigators to work alongside Mr Bristow with a specific focus on allegations of potential misconduct or gross misconduct."
The criminal investigation began in May after allegations against present and former members of Cleveland Police Authority (CPA).
A CPA spokesman said the decision to suspend the men was a "neutral act" which did not mean anything was proven against the two chief officers.
Mr Price has denied any wrongdoing and vowed to clear his name.
The IPCC is already independently investigating an allegation that Mr Price used undue influence to have an individual appointed to a position within the police force.
This investigation continues. All three have been released on bail until a date in October.